PROJECT SUMMARY/ABSTRACT: The purpose of this Pathway to Independence Award is to prepare the applicant for an independent, sustained program of research that incorporates biological, behavioral, and genetic concepts and methods to understand and prevent toxic stress among vulnerable children and families. Toxic stress describes persistent elevation of the hypothalamic-pituitary-adrenal (HPA) axis that occurs in response to childhood adversity (e.g. poverty, maltreatment, parental mental illness), can be buffered by supportive caregiving, and leads to poor health and development across the lifespan. Toxic stress can also be transmitted through generations, but the underlying mechanisms of transmission are poorly understood. The research conducted in this study builds on NIH- funded predoctoral research conducted by the applicant (F31NR016385), in which novel relationships between mothers' childhood history (adversity and family strengths), current caregiving (caregiving responsiveness and parental stress), and child indicators of toxic stress (biological, health, behavioral) were detected among multiethnic, low-income maternal-child-dyads. Based on the importance of consistent sleep and circadian rhythm patterns for healthy HPA-axis functioning, in the K99 phase the applicant will examine the feasibility of using mother-child dyad actigraphy data to measure consistent daily routines (e.g. regular bedtimes, physical activity) and test the hypothesis that caregivers can protect their children from toxic stress by providing daily routine consistency. The K99 phase will include training in concepts and methods related to sleep/circadian rhythm and gene-environment (GxE) interactions, as individuals are known to be differentially susceptible to the effects of early childhood experiences. This training will be supported by expert mentorship and tailored training experiences including coursework, directed readings, seminars, and scientific meetings. Informed by relationships detected in the F31 and K99 phases of the study, in the R00 phase the candidate will examine relationships among maternal childhood history, current maternal caregiving (consistent daily routines, caregiving responsiveness, parental stress) and child indicators of toxic stress in a fully-powered sample of multiethnic, low-income mother-child dyads (children age 3-4 years). Indicators of toxic stress will include biological markers (e.g. hair cortisol, salivary cytokines) with which the candidate has prior expertise. The candidate will also explore the extent to which genotypic variation in candidate genes related to caregiving (OXTR, DRD4) and stress (BDNF, IL-6, FTO) contribute to mothers' and children's susceptibility to the effects of early childhood experiences. The results of this study will be used by the candidate to further examine intergenerational transmission of toxic stress and protective factors, and ultimately develop a precision health intervention that aims to prevent toxic stress based on families' biobehavioral, genetic and environmental characteristics.